The present invention relates in general to extrusion casting and in particular to an adjustable sliding mold for use in an extrusion installation for producing continuous castings of a substantially rectangular cross section.
In order to change the cross section of a continuous casting, in prior-art extrusion installations it was necessary to install another sliding mold of the required clearance. As a consequence, it was necessary to provide for a relatively large stock of expensive slide molds made of copper, and usually provided with cooling passages. Moreover, the exchanging operation necessitated a relatively long shutdown of the extrusion installation.
From the Swiss patent CH-PS No. 386 629 (FIG. 5), an adjustable sliding mold of the aforedescribed kind is known. This prior-art slide mold consists of two relatively light walls arranged parallel to each other and of two mold parts arranged at right angles to the two walls so as to complete a rectangular cross section of the slide mold. The clearance between the mold parts is variable by means of a spindle-like adjusting device. By fixing the adjustable mold part in a desired position, it is possible to achieve in a relatively simple manner a convergence of the extrusion channel of the mold matching in the known manner the shrinkage of the continuous casting upon its solidification. In principle, it is also possible in this prior-art mold to adjust the mutual position of the mold parts in a relatively large range so as to produce in the same sliding mold both broad and narrow extruded strands.
Nevertheless, it has been found that such prior-art adjustable sliding molds are possessed with disadvantages, particularly regarding the leak-tightness between the contact surfaces of the movable and fixed parts of the adjustable mold. The four mating surfaces of the mold parts must be carefully machined with relatively large expenditures in order to ensure proper operation of the device. Another problem arises from the fact that the guiding of the movable mold parts at right angles to the fixed mold parts requires an extreme accuracy in manufacturing these component parts. It has been found that in spite of considerable efforts in machining, a certain amount of seizing or slipping can hardly be avoided, resulting in waste of material.